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Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
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Experimental and modeling analyses for interactions between graphene oxide and quartz sand
Jin-Kyu Kang1, Jeong-Ann Park2, In-Geol Yi1
1a Environmental Functional Materials and Water Treatment Laboratory , Seoul National University , Seoul , Korea.
Summary
Graphene oxide (GO) adhesion to quartz sand increases significantly with higher salt concentrations, especially calcium ions. This study quantifies GO-quartz interactions, showing reduced GO mobility in higher ionic strength solutions.
Area of Science:
- Environmental Science
- Materials Science
- Physical Chemistry
Background:
- Graphene oxide (GO) is a nanomaterial with potential environmental applications and risks.
- Understanding GO interactions with soil components like quartz sand is crucial for predicting its environmental fate.
- Ionic strength and specific ions significantly influence nanoparticle-soil interactions.
Purpose of the Study:
- To quantify the interactions between graphene oxide (GO) and quartz sand under varying ionic conditions.
- To elucidate the mechanisms governing GO adhesion and mobility in porous media.
- To compare the effects of different cations (Na+, Ca2+) and surface coatings on GO transport.
Main Methods:
- Experimental analyses including zeta potential measurements and column experiments.
- Modeling analyses using Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and Maxwell models.
- Investigation of GO transport in quartz sand and aluminum oxide-coated sand under different NaCl and CaCl2 concentrations.
Main Results:
- Both GO and quartz sand exhibit negative surface charges in NaCl and CaCl2 solutions.
- GO adhesion to quartz sand is highly favorable at increased NaCl concentrations (≥50 mM) and with 5 mM CaCl2, indicated by lowered energy barriers and increased attachment probabilities.
- Mass removal of GO increased from 5.4% to 97.8% with rising NaCl concentration; CaCl2 (5 mM) resulted in 100% removal, showing stronger Ca2+ influence than Na+.
Conclusions:
- Increasing ionic strength, particularly with divalent cations like Ca2+, significantly enhances graphene oxide retention in quartz sand.
- The findings highlight the critical role of solution chemistry in controlling GO mobility and fate in subsurface environments.
- GO mobility is lower than chloride but higher than multi-walled carbon nanotubes, and is reduced by aluminum oxide coatings on sand.
